Protection against momentary loss of track circuit shunt



April 23, 1957 A. E. 0050 2,790,070

PROTECTION AGAINST MOMENTARY LOSS OF TRACK cmcun SHUNT Filed Jan. 27, 1951 p i c I ;'-L to j ,2 1 m i BX NX INVENTOR.

' rtlmrlifladd HIS ATTORNEY 2,790,070 p n I PROTECTION AGAINST 'MOME'NTARY L :1 TRACK'CIRCUIT SHUNT 'ArthurEDodd, Edgewood Pag assignor to Westingh'euse CC .vv

leasing by an'ener'gy storing device connectedinmultiple with thecontrol winding of the first repeater're1ay,"-is the 1 provision of a second 'repea terr'elay, whichfniay be" off the slow? pickup type, having a make-before-break front and back contact, and having stick and pickup circuits controlled'by the make-before-break contact-and by fr'ont Air Brake Company, a ccarponratirur of Pennsylvania f p Application January 27, 19 1,saia'Ns; 0t, t1

' '10 Claims. (crime-'34 My invention relates'to protection against momentary los's 'of track circuitshun n More particularlyn 'my invena tion relates to apparatus for preventing false operatioini of railway' traflic controlling appa'ratu tary loss of track circuit shunt. Track circuit control of railw s due to a momenay tr aiiic' controlling rap paratus, such, fo r example, as signals and trackiswitches, :11 is based'on the principle that whena train 'or' oth'er railv; way ve' hicle'ienters upon a tracksection; the railsof WhIChJ i.

are includedin a track circuitin series with amen relay,-/ 1

a plurality of-shu'nt paths, one through'each'pair of 'wheels and thehssociated axle, will be completed across'the track circuit; and that such-shunting of the track circuit will be effective to deenergizefthe'track relay so :that. its 'front'contactswill become opened and its back icon-: 1

tacts will become closed, and will remain in that 'condition' as long as any one ofthe' pairs of Wheels remains on the track section. It has "been foundphoweverg that "T under some conditionstsuch,for example, as whenzthe rails have become rusty 01 Wh11 there is' some material'i.

such,-for example, as sand on the rails, rther'e maybe a momentary loss :of shunt of the track circuitiso that'thei track relay may become energized and open its :back con 'rv tacts and close its front contacts While' one pairs'of wheels remain on the tracksectionl. 11-; t

A'railwaysignal for governing trafli'cimovementsxfove such a track. section, particularly ifit is'tof a 'qnick:actin type such, for example, as a.light=signal, "if controlle r directly by a front contact of :the'track relay; might therefore display: a proceed'indication for a brief 'periodn'l of timegduring a momentary loss of shuntiof theitrack circuit. Obviously, it would he a dangerous conditional if a'signal' for 'a track section displayed a proceed-indica-' tion for even a brief period of time whileithe associate track section is occnpiedbya caror train 1 An object of myinvention', therefore, is to' provide pro apparatus for the track section, such,- for example-{as ,a

track switch,lwi1l not be falsely operated, becausegof a momentary. loss of track circuit shunt. v

Afeature of 'my invention for, attaining "t is the'provision of a first repeater relay,'arranged to bc,,

slowireleasing, controlledby a back co'ntact'ofa track relay, a s'ec'ondn'repeater relay, which may be of a-slow: pickup type, having a'pi'ckup circuit controlledby a-front contact of the" first repeater relay, and having: a stick circuit controlled-by alfront contact of the track rrelay' and 'by a front contact of the second 'repeater relay,' ';and

trafiic governing means controlled-"by a back contact of the first repeater relayian second repeater'relay' Anotherfeature of my invention for attain ngthr object; in? an arrangementin which a first; or back tact repeater relay for a track' relayis rendered 'slow"re-' d by ansteamer 'of the u contacts of the rtrack're'lay' and the 'first repcatef "relay, andthe provision of control means for a traffic gov'ernf ingdeviceiincluding' a 'back contact iofthe first repeater relay and a. from contact 'of the second"r ep eatei" relay; Iishalldescribe one formfof apparatus embodying my"? point out the novelt features invention, and shall then thereof in claims; p

The accompanying drawing -is-'-a'"d :Iin an "arrangementhaving a slowreleasingfirst or back contact'repeater 'relayTPB for atrafficfre sponsive relay 5 suchpfor example, as 'a track" relay TR; which includes 1 a second repeate'r relay'TP,"of7the 'slow pickup type," having azamake-before-break contact- '10;"'w'hich includes;

s'tick and: pickup circ'uitsfof "the second repeater relay controlled 'by'front and back" points of' -the" makefbeforebreak contact'and by front contacts of thef track 'relay' and-the first ire'peaterl'relay; "and which includf trafiic governing means such, for examplef-as ia 'sig'naIIS conj" trolled T by, a back contact 11 'of the first repeaterrelay and: by ai-fronfcontact "12 of the second repeater: re1ay.*

nce characters"refer"to similar part '11 Similar. refere the-drawings Referringfui'ther therrail'sladjacent thefoppositeend 6f thf g'cjtin I shown'in the dr'awing, which Ifshall- -assu 1ne"is" the bound direction. A second signal, designatedby; "erence character 2S,-is locatedadja'c oppositefor westbound direction over section I. 5 Signals 1S-and ZS-"may be. 'offany"s uitab1e 'design'such, for e ample, as the Well-known colorlight'or"searchlight typ A first, or back contact, rep'eater' angaesrgmea by b sis,

the reference {character TPByis controlle' contactofztrack'relayTR. Relay TPB is r leasin'g by' a resistor, des'ignate'chby the reference acter r, and an energy storing device shown as a capacitor, v

' designated f b the reference; character 6,", connected ,in

series with each other around-the winding 'offrelay TPB; Relay IPB and ica'pacitorfc are at timesene'rgized, in mu'ltiple 'with each other',f by currntffronra suitable a POSP',"

sourt'teys'uch, forlexamp le, as a' battery Q, having 'tive terminal B; and a' negative terns-main;

A second; or front contact, repeated rela which becomes closed at a front point-befo r' openedf the back point, whe'iifrelayTl r energiiing circuit, referred to as an operating circuit, for relay Patented "Apr-r 23,

iagranimaticwiew showing one form of apparatus "embodying'my' invention;

to the drawing, a stretcher railway track fis shown, 'over which trains may nermttnym ve; in either direction; Rails 3 and saof'the'stretch of track aredivided by'insulated joints 4 to'fofm-a tracbsection T. -rSecti'0n .T 'is provided with a track' circuit which in cludes rails 3 and 3a of the 'sectionand a suit'a' ble' scarce 'ofcurrent such, for'exam'ple, as 'a secondary winding' dof atrack transformer, designated thereference'chan" acter'F, connected across 'the'railsadjacent {one endflof the section, and also a track relay 1TRconneeted across A: signal, designated by the reference" character-1s; 1s located adjacent the relay end 'a of s'e'ction T,' f dr g vrninglti'afficmovements oversection T towar the rightjas' esi gna'ted bygthejreference character TP,--isjfof a-slo w-pickup and' op'erates a contact 10 of awen ewn rorni rsswn;

as a make-before-break, or continuity,-'co ta'Ctjwhichis chased at a back point, while relay'TPfisdeiiergiied, and

its control winding, and is supplied with energizing current from capacitor through resistor r, through front contacts 8 and 9 of relays TR and T PB, respectively, and through the back point of contact 10 of relay TP. A stick, or retaining, circuit for relay TP includes its control Winding, and is supplied with energizing current passing from battery Q, through the front point of a contact 7 of relay TR, and through the front point of contact 10 of relay TP.-

Alternating current is supplied by a suitable source such, for example, as an alternating current generator, designated by the reference character G, over a pair of line conductors or terminals, designated by the reference characters BX and NX. The primary winding m of track transformer F is energized by current from terminals BX and NX.

It is obvious that direct current may be applied directly to therails 3 and 3a from a suitable source of direct current in which case transformer F would be omitted.

As here shown, track relay TR is of a two-element alternating current type, having a track winding connected to the rails 3 and 3a of section T, and having a line control winding 11. Line control winding h is energized by current from terminals BX and NX over contact 5 of relay TR or over contact 6 of relay TPB. It is obvious toanyone skilled in the art that a direct current relay may readily be used in place of the two element alternating current relay shown if the track circuit is energized 7 from a direct current source.

The purpose of this control ofline control winding h of relay TR is to prevent a locked-out condition of relay TP, in the event of a partial shunt of track section T which, on account of relay TR being of an alternating current type, might cause contact 7 of relay TR to become opened at its front point, deenergizing relay TP, and to then fioatfor a brief period of time between its front and back points, and to then again become closed at its front point without becoming closed at its back point. If contact 7 of relay TR did not become closed at its back point after becoming opened at its front point and thereby deenergizing relay TP, relay TPB would not become energized, and relay TP would therefore remain deenergized after relay TR again became energized.

The phenomenon of floating occurs only under a relatively restricted combination of conditions which rarely occurtogether so that a single winding relay could be used but I prefer to employ a two winding relay with an alternating current track circuit to avoid any possibility of a locked-out condition.

A circuitfor controlling signal TS to normally display a proceed indication includes a back contact 11 of relay TPB and a front contact 12 of relay Tl. A circuit for controlling signal 28 to normally display a proceed indication, similarly includes a back contact 13 of relay TPB and a front contact 14 of relay TP.

Having described, in general, the arrangement and control of the various parts of apparatus embodying my invention, I shall now describe the circuits and operation in detail.

As shown in the drawing, all parts are in the normal condition, that is, track section T is unoccupied, and therefore track relay TR is energized; relay TP is energized by its retaining circuit; relay TPB is deenergized; capacitor c is in the discharged condition; and signals 18 and 28 are displaying a proceed indication.

A stick circuit, by which the line control element or Winding h of relay TR is energized, passes from terminal BX, through contact 5 of relay TR, and winding 11 of relay TR to terminal NX. v

I shall assume that, with apparatus embodying my invention, as shown in the accompanying drawing, an eastbound trainpasses signal 18 onto track section T, deenergizing relay TR. With relay TR deenergized, its Contact 5 will be open in the circuit previously traced for winding h of relay TR.

With relay TR deenergized, the retaining circuit for relay TP will be opened at the front point of contact 7 of relay TR, :so that relay TP will be deenergized and its contacts 12 and 14 will open the circuits for signals 18 and 25, respectively, causing signals 18 and 28 to cease to display a proceed indication. With relay TR deenergized, relay TPB will become energized by a circuit passing from terminal B, through the back point of contact 7 of relay TR, the winding of relay TPB in multiple with a path through resistor r, and capacitor 0, to terminal N.

When relay TPB becomes energized, a pickup circuit will be completed for winding h of relay TR, this circuit passing from terminal BX, through contact 6 of relay TPB, and winding h of relay TR to terminal NX. Relay TR will, however, not become operated, for opening its back contact and closing its front contacts, as long as track section T is occupied by the train.

When the train leaves section T, relay TR, on account of its pickup circuit just traced being completed, will again become energized, thereupon opening the circuit traced for relay TPB, at the back point of contact 7.

Relay TPB is, however, slow releasing, on account of' resistor r and capacitor c being connected around its control winding, and therefore relay TPB will not at once release its contacts 9, 11 and 13 to permit contact 9 toopen and contacts 11 and 13 to close. During the release period of relay TPB, while contact 9 of relay TPB remains closed, relay TP will become energized by a pickup circuit passing from capacitor 0, through resistor r, contacts 8 and 9 of relays TR and TPB, respectively, contact 10 of relay TP closed at its back point, the winding of relay TP, and terminal N back to capacitor 0. Contact 10 of relay TP will then start to move from its back point toward its front point.

Before contact 10 becomes opened at its back point, it will become closed at its front point, thereby completing, for a brief period of time, a second energizing circuit for capacitor c and relay TPB, this circuit passing from terminal B, through the front point of contact 7 of relay TR, front point of contact 19 of relay TP, back point of contact 10 of relay TP, contact 9 of relay TPB, contact 8 of relay TR, and winding of relay TPB connected in multiple with the path through resistor r and capacitor 0 to terminal N. This second energizing circuit for relay TPB and capacitor c serves to increase the release period for relay TPB.

When contact 10 of relay TP becomes closed at its front point, the stick circuit will be completed for relay TP, this circuit passing from terminal B, through the front point of contact 7 of relay TR, the front point of contact 10 of relay TP, and the winding of relay TP to terminal N.

At the end of the release period of relay TPB, its contacts 6 and 9 will become open, and its contacts 11 and 13 will become closed. With contact 6 open, the pickup circuit previously traced for winding h of relay TR will be opened, but the stick circuit for winding 11 through contact 5 of relay TR will then be closed, so that relay TR will remain energized. With contact 9 of relay TPB open, the pickup circuit for relay TP will be open at contact 9 as well as at the back point of contact 10 of relay TP, but relay TP will then remain energized by its stick circuit previously traced. The release period for relay TPB may be arranged to be of the order of 15 seconds, during which relay TP will become operated and completeits stick circuit.

With relay TP again energized, and relay TPB again deenergized, the circuits previously described for controlling signals 1S and 28 to display a proceed indication will again be completed.

As I have already stated, relay TPB is made slow releasing by resistor r and capacitor c connected in series with each other around the winding of relay TPB, and also by the circuit closed through the front andv back points I of contact 10 of relay TP while contact 10 of relay FF is moving from its back to its front, point. The values of resistor r and capacitor and the length of the pickup time of relay TP may be selected so thatfthe release time of relay TPB may, for example, be of the orderof seconds.

Relay TP, on account of its pickupJciriiuitbeing controlled by a front contact of relay TPB, checks that relay TPB is not disconnected from its energizing circuit. Relay '1 P, on account of being'energ'ized by capacitor 0, checks that capacitor c is not disconnected and that it has not become defective. If capacitor 0 should become disconnected or should become'defectivefrelay TP would not, receive sufficient energy from capacitor 0 to causerelay TP to pick up. furthermore, if capacitor. c should become disconnectedxor defective, relay TPB would release so quickly that there would not be time forrelay TP to pick up. Relay TP, therefore, also checks that relay TPB has a sufficiently long release period to bridge a momentary loss of track circuit shunt, so that signals 18 and 28 cannot become falsely operated to display a proceed indication because of a momentary loss pf shunt of track section T. On account of signals 1S and 28 being controlled by front contactsof relay TP, the pickup circuit of which is controlled by a frontcontact of relay TPB, these signals cannot be controlled to display a proceed indication if relay TPB should become disconnected and therefore remain deenergized.

I shall now assume that, with apparatus arranged as shown in the drawing, an eastbound train enters sec tion T, deenergizing relay TR and thereby causing relay TPB to become energized, as previously, described. I shall assume further that there is a momentary lossof shunt of the track circuit for section T, so that relay TR picks up for a brief period of time. Relay TP, being of the slow pickup type, will not'close its front contacts until after the lapse of a measured period of time, during which the track shunt will probably be again restored. If, however, the loss of shunt should be long enough for relay TP to close its stick circuit through the front point of contact 10, relay TPB would still retain its contact 9 closed and its contacts 11 and 13 open, and would therefore bridge any momentary loss of shunt. The circuits for signals 18 and 28 would therefore remain open at the back contacts 11 and 13, respectively, of relay TPB, and at the front contacts 12 and 14, respectively, of relay TP, or at only the back contacts 11 and 13 of relay TPB during a momentary loss of shunt.

It follows that, in apparatus embodying my invention, signals 18 and 28 would not be controlled to display a proceed indication falsely because of a momentary loss of shunt of track section T. Apparatus embodying my invention therefore provides protection against false operation of railway traflic controlling apparatus, such,

for example, as a railway signal, duringmomentary' loss of shunt of a track circuit over whichthe signal governs traffic movements. t j t Although I have herein shownand described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims Without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: 1. In a railway trafiic controlling arrangement. in which a first repeater relay is controlled by a track relay in the deenergized condition and is rendered slow releasing by an energy storing device connected in multiple with the control winding of said firstrepeater relay, the combination comprising, a second repeater relay of the slow pickup type having a make-before-break contact which is closed at a back point While the corre- 'sponding relay is deenergized and which becomes closed at a front point beforebecoming opened at said back point when the corresponding relay becomes energized,

a pickup circuit for saidsecond repeater relay'energize d by said energy storing device and including a front conftact of said track relay and a front contact of said first;

repeater relay and also including said make-before-break contact closed at the back point, a stick circuit for said second repeater relay energized by a suitable source of current and including a front contact of said track relay and also including said make-before-break contact closed at theflfront point, and traffic governing means controlled by a back contact of said first repeater relay and by a] front contact of said second repeater relay. H

, 2. In combination, a section of railway track, a track relay having a first and a second winding, a source of alternating current, a track circuit for said section in-, cluding the rails of said section and the first winding or said track 'relay and also said source of alternating cur rent, a first repeater relay, an energy storing device, a' source of direct current, a circuit energized by said source of direct current and controlled by said track relay in the deenergized condition for energizing said first repeater relay and said energy storing device in multiple with each other, a circuit including a contact of the first repeater relay for energizing the second winding of the track relay, a stick circuit forthe second winding of the track relay including a front contact of the track relay, a second repeater relay of the slow pickup type havinga make-beforebreak contact which is closed at a back point while the corresponding relay is deenergized and which becomes closed at a front point before becoming opened at said back point when the corresponding relay becomes energized, a pickup circuit for said second repeater relay energized'by said energy storing device and including a front contact of said track relay and a front contact of said first repeater relay and also including said make-before-break contact closed at the back point, a stick circuit for said second repeater relay energized by the source of direct current and including a front contact of said track relay and also including said make-before-break contact closedat the front point, and traffic governing means controlled by a back contact of said first repeater relay and by a front contact of said second repeater relay.

3. In combination, a stretch of railway track, a source of current, a traflic responsive relay normally energized by said source of current while said stretch of track is unoccupied and becoming deenergized in response to a train occupying said stretch of track, a first repeater relay, an energy storing device, means controlled by said trafiic responsive relay in the deenergized condition for effecting energization of said first repeater relay in multiple with said energy storing device, a second repeater relay of a slow pickup type having a make-beforebreak contact which is closed at a back point while the corresponding relay is deenergized and which becomes closed at a front point before becoming opened at said back point when the corresponding relay becomes energized, a pickup circuit for said second repeater relay energized by said energy storing device and controlled by said track relay and said first repeater relay. in an en: ergized condition and by said make-before-break contact closed at its back point, a second source of current, a stick circuit for said second repeater relay energized by said second source of current and controlled by said traffic responsive relay in an energized condition and by said make-before-break contact closed at its from point, and traflic governing means controlled by said first repeater relay in the deenergized condition and by said second repeater relay in an energized condition. I t

4. In combination, a stretch of railway track, a source of current, a traffic responsive relay normally energized by said source of current while said stretch of track is unoccupied -but becoming deenergized in re-. sponse to a train occupying said stretch of track, a first repeater relay, an energy storing device, means controlled by aback contact of said traffic responsive relay for energizing said first repeater relay in multiple with said energy storing device, a second repeater relay of a slow pickup type having a make-before-break contact which is closed at a back point while the second repeater relay is deenergized and Which' becomes closed at a front point before becoming opened at said back point when the second repeater relay becomes energized, a pickup circuit for said second repeater relay energized by said energy storing device and controlled by front contacts of said track relay and said first repeater relay and by said make-before-break contact closed at its back point, a second source of current, a stick circuit for said second repeater relay energized by said second source of current and controlled by a front contact of said traffic responsive relay and by said make-before-break contact closed at its front point, and traffic governing means controlled by a back contact of said first repeater relay and by a front contact of said second repeater relay.

5; In combination, a stretch of railway track, a source of current, a traffic responsive relay normally energized by said source of current while said stretch of track is unoccupied but becoming deenergized in response to a train occupying said stretch of track, a first repeater relay, an energy storing device connected in multiple with said first repeater relay to thereby render the first repeater relay slow-releasing, means controlled by a back contact of said traffic responsive relay for energizing said first repeater relay in multiple with said energy storing device, a second repeater relay of a slow pickup type having a back contact which is closed while said second repeater relay is deenergized and having a front contact which becomes closed before said back contact becomes opened when said second repeater relay becomes energized, a pickup circuit for said second repeater relay energized by said energy storing device and controlled by front contacts of said traffic responsive relay and said first repeater relay and by said back contact of said second repeater relay, circuit means including the front contact of the second repeater relay and the back contact thereof during the time when both said front and back contacts of the second repeater relay are closed for energizing said energy storing device to thereby further increase the release time of the first repeater relay, a stick circuit for said second repeater relay energized by a suitable source of current and controlled by a front contact of said traffic responsive relay and by said front contact of said second repeater relay, and triific governing means controlled by a back contact of said first repeater relay and by a front contact of said second repeater relay.

6. In combination, a stretch of railway track, a source of current, a trafiic responsive relay normally energized by said source of current while said stretch of track is un- Occupied but becoming deenergized in response to a train occupying said stretch of track, a slow releasing first repeater relay, an energy storing device, means controlled by said trafiic responsive relay in the deenergized conditron for energizing said first repeater relay in multiple with said energy storing device, a second repeater relay of a slow pickup type having a back contact which is closed while said second repeater relay is deenergized and having a front contact which becomes closed before said back contact becomes opened when said second repeater relay becomes energized, a pickup circuit for said second repeater relay energized by said energy storing device and controlled by said trafi'lc responsive relay in an energized condition and by said back contact of said second repeater relay; circuit means including said front and back contacts of the second repeater relay in series for energizing the'energy storing means, the first repeater relay and the second repeater relay all in multiple; a stick cir- F cuit for said second repeater relay energized by a suitable source of'current and controlled by said traffic responsive relay in'an energized condition and by said front contact of said second repeater relay, and traffic governing means controlled by said first repeater relay in the deenergized 8 condition and by said second repeater relay in an energized condition.

7. In combination, a stretch of railway track, a source of current, a traffic responsive relay normally energized by said source of current While said stretch of track is unoccupied but becoming deenergized in response to a train occupying said stretch of track, a first repeater relay, an energy storing device, means controlled by said traffic responsive relay in the deenergized condition for energizing said first repeater relay in multiple with said energy storing device, a second repeater relay having a back contact which is closed while said second repeater relay is deenergized and having a front contact which becomes closed before said back contact opens when said second repeater relay becomes energized, a pickup circuit for said second repeater relay energized by said energy storing device and controlled by said traffic responsive relay and said first repeater relay inan energized condition and by said back contact of said second repeater relay, a stick circuit for said second repeater relay energized by a suitable source of current and controlled by said trafiic responsive relay in an energized condition and by said front contact of said second repeater relay, and traffic governing means controlled by said first and second repeater relays.

8. In combination, a stretch of railway track, a source of current, a traffic responsive relay normally energized by said source of current while said stretch of track is unoccupied but becoming deenergized in response to a train occupying said stretch of track, a first repeater relay arranged to be slow releasing, means controlled by said trafiic responsive relay in the deenergized condition for controlling said first repeater relay, a second repeater relay of a slow pickup type, a pickup circuit for said second repeater relay controlled by means including front contacts of said trafiic responsive relay and of said first repeater relay, a stick circuit for said second repeater relay controlled by front contacts of said traflic responsive relay and of said second repeater relay, and traffic governing means controlled by said first repeater relay in the deenergized condition and by said second repeater relay in an energized condition.

9. In combination, a stretch of railway track, a source of current, a traflic responsive relay normally energized by said source of current while said stretch of track is unoccupied but becoming deenergized in response to a train occupying said stretch of track, a first repeater relay arranged to be slow releasing, means including a back contact of said trafiic responsive relay for controlling said first repeater relay, a second repeater relay; a pickup circuit for said second repeater relay controlled by means including, in series, front contacts of said traffic responsive relay and of said first repeater relay and a back contact of said second repeater relay; a stick circuit for said second repeater relay controlled by front contacts of said traffic responsive relay and said second repeater relay, and traffic governing means controlled by a back contact of said first repeater relay and by a front contact of said second repeater relay.

10. In combination, a stretch of railway track, a source of current, a trafiic responsive relay normally energized by said source of current while said stretch of track is unoccupied but becoming deenergized in response to a train occupying said stretch of track, a first repeater relay arranged to be slow releasing, means including a back contact of said traffic responsive relay for controlling said first repeater relay, a second repeater relay, a pickup circuit for said second repeater relay controlled by means including a front contact of said first repeater relay, a stick circuit for said second repeater relay controlled by front contacts of said traffic responsive relay and said second repeater relay, and traffic governing References Cited in the file of this patent UNITED STATES PATENTS Young et al Oct. 23, 1928 10 Dodd Dec. 8, 1936 Martin Jan. 4, 1938 Hitchcock July 26, 1938 Sorensen July 4, 1939 Hays Nov. 27, 1945 Thompson Feb. 8, 1949 Thompson Feb. 28, 1950 

